[pbhjpbhj]

The key value is in avoidance of loss (burglary), not in needing to get a new key cut.

Losing a key means changing the locks, the more duplicate keys the higher the cost.

[ebg13]

Except that getting the key back still means changing the locks because the finder could have duplicated it, so it seems like there's not a lot of value in giving it back except in the case that it's their only copy that they will use until they change the lock.